One of the most common distinctions that physicians make in seeing patients with complaints of memory trouble is the distinction between dementia and depression. Before I continue, I would once again like to distinguish between the terms dementia and Alzheimer's disease.
Dementia is a brain problem that includes impairment of memory and one or more other cognitive (thinking and reasoning) abilities. Alzheimer's disease is the most common, but not the only, late life cause of dementia. It has certain distinguishing characteristics and our accuracy at diagnosing Alzheimer's it is usually better than 80 percent. However, only knowledge of actual brain tissue changes allows us to make a definite diagnosis of Alzheimer's disease.
For today's discussion, I will contrast depression with dementias in general and at times with Alzheimer's disease specifically.
Depression and dementia are both relatively common problems. They both may be associated with impairments of thinking in memory. The impairments of thinking and memory from either of these disorders can be disruptive to daily activity performance. At first, we might question how depression and dementia might be confused.
We tend to think of depression as a change in mood with sadness and diminished interest in activities. Associated with this, the depressed person commonly has impairments in performing activities. When this group of symptoms is the primary presentation, the diagnosis may be relatively easy. However, especially in older individuals, depression may have less mood change but significant impairments in performing activities. If such is the case, depression might be mistaken for dementia, including Alzheimer's disease. Depression and dementia may also occur together in the same person. A person with early Alzheimer's disease may react to their dementia with the degree of depression.
One situation in which this problem of distinguishing depression from dementia may occur is the following: A person may present to a doctor with complaints of difficulty doing things, be aware that they have some difficulty with memory, and believe they have early dementia. The medical assessment then must evaluate the person for dementia and depression. This medical assessment will typically include the history and examination, but also may include psychological or neuropsychological assessment and possibly neurological tests.
The medical treatments of dementia and depression are clearly different. In a previous blog I have discussed medical treatments in dementia. Medical treatments of depression include a large number of medications from which the physician must choose the medication that is best suited to the individual patient.
In summary, not every person who has impairment of thinking and memory has dementia. Depression is relatively common, may not have the associated changes in mood typical for that disorder, and may be associated with difficulties in thinking and memory. The presence of depression as a cause for difficulty with thinking and memory does not exclude the presence of dementia. However, when depression is present, with or without dementia is an important and treatable diagnosis.